A scintillator is a material that can absorb high-energy particles and convert these particles to multiple low-energy photons. Scintillation materials are scientifically and economically significant in conjunction with photodetectors to detect high-energy photons, electrons and other particles in various applications, which include medical imaging, geological exploration, homeland security, and high-energy physics. In order to maximize the scintillator's values in the applications, characteristics including high scintillation light yield, fast scintillation decay time and rise time, good energy resolution, high degree of proportionality, proper emission wavelength, and good thermal response over a wide temperature range are desired. To these ends, it is important to obtain electron/hole traps and defect free scintillators.
Elpasolite scintillators are a promising class of scintillators, with good scintillation properties and symmetric structure. For example, Cs2LiYCl6 doped with cerium scintillators are fabricated and used as gamma-ray and neutron detectors, as described in “Optical and scintillation properties of Cs2LiYCl6:Ce3+ and Cs2LiYCl6:Pr3+ crystals,” by E. Van Loef et al., IEEE Transactions on Nuclear Science, 2005, 52, 1819-1822. In addition, Cs2LiYCl6 doped with cerium also has nearly perfect proportionality response. As another example, in “Selected Properties of Cs2LiYCl6, Cs2LiLaCl6, and Cs2LiLaYBr6 Scintillators,” IEEE Transactions on Nuclear Science, 2011, 58, 333-338, Glodo et al. reported the scintillation properties of Cs2LiLaCl6 and Cs2LiLaBr6 doped with cerium single crystals. In addition, Combes et al. reported the scintillation properties of undoped Cs2LiYCl6 in “Optical and scintillation properties of pure and Ce3+-doped Cs2LiYCl6 and Li3YCl6:Ce3+ crystals,” Journal of Luminescence, 1999, 82, 299-305. In a further example, General Electric Company filed a patent application covering cerium doped elpasolite halides scintillators, titled “Activated mixed halide elpasolites and high energy resolution scintillator” and published as U.S. Patent App. Pub. No. US 2013/0126741.
Common dopants used to externally activate scintillation compounds include Ce3+, Pr3+, Eu2+, In+, Na+ and Tl+. However, the limitations of externally activated scintillators have been recognized, as noted in “Fundamental Limitations in the Performance of Ce3+, Pr3+, and Eu2+ Activated Scintillators,” by Dorenbos, IEEE Transactions on Nuclear Science, 2010, 57 (3), 1162-1167. In addition, the use of dopants increases material, manufacturing, and production costs, and as these materials may be highly reactive or toxic, special safety and handling procedures are often required.